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Special Conditions: Cirrus Design Corporation Model SF50 Airplane; Full Authority Digital Engine Control (FADEC) System

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Information about this document as published in the Federal Register.

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Federal Aviation Administration (FAA), DOT.


Final special conditions; request for comments.


These special conditions are issued for the Cirrus Design Corporation model SF50 airplane. This airplane will have a novel or unusual design feature(s) associated with the use of an electronic engine control system instead of a traditional mechanical control system. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for this design feature. These special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards.


The effective date of these special conditions is April 12, 2010.

We must receive your comments by May 20, 2010.


Mail two copies of your comments to: Federal Aviation Administration, Regional Counsel, ACE-7, Attn: Rules Docket No. CE306, 901 Locust, Kansas City, MO 64106. You may deliver two copies to the Regional Counsel at the above address. Mark your comments: Docket No. CE306. You may inspect comments in the Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.

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Peter L. Rouse, Federal Aviation Administration, Aircraft Certification Service, Small Airplane Directorate, ACE-111, 901 Locust, Room 301, Kansas City, Missouri 64106; 816-329-4135, fax 816-329-4090.

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The FAA has determined that notice and opportunity for prior public comment hereon are impracticable because these procedures would significantly delay issuance of the design approval and thus delivery of the affected aircraft. In addition, the substance of these special conditions has been subject to the public comment process in several prior instances with no substantive comments Start Printed Page 20519received. The FAA therefore finds that good cause exists for making these special conditions effective upon issuance.

Comments Invited

Interested persons are invited to submit such written data, views, or arguments as they may desire. Communications should identify the regulatory docket or special condition number and be submitted in duplicate to the address specified above. All communications received on or before the closing date for comments will be considered by the Administrator. The special conditions may be changed in light of the comments received.

All comments received will be available in the Rules Docket for examination by interested persons, both before and after the closing date for comments. A report summarizing each substantive public contact with FAA personnel concerning this rulemaking will be filed in the docket.

Commenters' wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must include a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket No. CE306.” The postcard will be date stamped and returned to the commenter.


On September 9, 2008, Cirrus Design Corporation applied for a type certificate for their new model SF50. The Cirrus Design Corporation model SF50 is a low-wing, five-plus-two-place (2 children), single-engine turbofan-powered aircraft. It incorporates an Electronic Flight Information System (EFIS), pressurized cabin, retractable gear, and a V-tail. The turbofan engine is mounted on the upper fuselage/tail cone along the aircraft centerline. It is constructed largely of carbon and fiberglass composite materials. Like other Cirrus products, the SF50 includes a ballistically deployed airframe parachute.

The model SF50 has a maximum operating altitude of 28,000 feet, where it cruises at speeds up to 300 KTAS. Its VMO will not exceed 0.62 Mach. The maximum takeoff weight will be at or below 6000 lbs with a range at economy cruise of roughly 1000 nm. Cirrus intends for the model SF50 to be certified for single-pilot operations under 14 CFR part 91 and 14 CFR part 135 operating rules. The following operating conditions will be included:

  • Day and Night VFR.
  • IFR.
  • Flight Into Known Icing.

The Cirrus Design Corporation model SF50 airplane is equipped with a Williams International FJ33-5A turbofan engine using an electronic engine control system (FADEC) instead of a traditional mechanical control system. Even though the engine control system will be certificated as part of the engine, the installation of an engine with an electronic control system requires evaluation due to critical environmental effects and possible effects on or by other airplane systems, for example, indirect effects of lightning, radio interference with other airplane electronic systems, shared engine and airplane data and power sources.

The regulatory requirements in 14 CFR part 23 for evaluating the installation of complex systems, including electronic systems and critical environmental effects, are contained in § 23.1309. However, when § 23.1309 was developed, the use of electronic control systems for engines was not envisioned. Therefore, the § 23.1309 requirements were not applicable to systems certificated as part of the engine (reference § 23.1309(f)(1)). Parts of the system that are not certificated with the engine could be evaluated using the criteria of § 23.1309. However, the integral nature of these systems makes it unfeasible to evaluate the airplane portion of the system without including the engine portion of the system.

In some cases, the airplane that the engine is used in will determine a higher classification than the engine controls are certificated for, requiring the FADEC systems be analyzed at a higher classification. As of November 2005, FADEC special conditions mandated the classification for 23.1309 analysis for loss of FADEC control as catastrophic for any airplane. This is not to imply an engine failure is classified as catastrophic, but that the digital engine control must provide an equivalent reliability to mechanical engine controls.

Type Certification Basis

Under the provisions of 14 CFR part 21, § 21.17, Cirrus Design Corporation must show that the model SF50 meets the applicable provisions of part 23, as amended by Amendments 23-1 through 23-59, thereto.

If the Administrator finds that the applicable airworthiness regulations (i.e., part 23) do not contain adequate or appropriate safety standards for the model SF50 because of a novel or unusual design feature, special conditions are prescribed under the provisions of § 21.16.

In addition to the applicable airworthiness regulations and special conditions, the model SF50 must comply with the fuel vent and exhaust emission requirements of 14 CFR part 34 and the noise certification requirements of 14 CFR part 36. Also, the FAA must issue a finding of regulatory adequacy pursuant to § 611 of Public Law 92-574, the “Noise Control Act of 1972.”

Special conditions, as appropriate, as defined in 11.19, are issued in accordance with § 11.38, and become part of the type certification basis in accordance with § 21.17(a)(2).

Special conditions are initially applicable to the model for which they are issued. Should the type certificate for that model be amended later to include any other model that incorporates the same novel or unusual design feature, the special conditions would also apply to the other model under the provisions of § 21.101(a)(1).

Novel or Unusual Design Features

The Cirrus Design Corporation model SF50 will incorporate the following novel or unusual design features:

Electronic engine control system.


As discussed above, these special conditions are applicable to the model SF50. Should Cirrus Design Corporation apply at a later date for a change to the type certificate to include another model incorporating the same novel or unusual design feature, the special conditions would apply to that model as well as under the provisions of § 21.101(a)(1).


This action affects only certain novel or unusual design features on the model SF50 airplanes. It is not a rule of general applicability and it affects only the applicant who applied to the FAA for approval of these features on the airplane.

Under standard practice, the effective date of final special conditions would be 30 days after the date of publication in the Federal Register; however, as the certification date for the Cirrus Design Corporation model SF50 is imminent, the FAA finds that good cause exists to make these special conditions effective upon issuance.

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List of Subjects in 14 CFR Part 23

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The authority citation for these special conditions is as follows:

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Start Printed Page 20520 Authority: 49 U.S.C. 106(g), 40113 and 44701; 14 CFR 21.16 and 21.17; and 14 CFR 11.38 and 11.19.

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The Special Conditions

Accordingly, pursuant to the authority delegated to me by the Administrator, the following special conditions are issued as part of the type certification basis for Cirrus Design Corporation model SF50 airplanes.

1. Electronic Engine Control

The installation of the electronic engine control system must comply with the requirements of 14 CFR 23.1309(a) through (e) at Amendment 23-49. The intent of this requirement is not to reevaluate the inherent hardware reliability of the control itself, but rather determine the effects, including environmental effects addressed in 14 CFR 23.1309(e), on the airplane systems and engine control system when installing the control on the airplane. When appropriate, engine certification data may be used when showing compliance with this requirement; however, the effects of the installation on this data must be addressed.

For these evaluations, the loss of FADEC control will be analyzed utilizing the threat levels associated with a catastrophic failure.

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Issued in Kansas City, Missouri, on April 12, 2010.

Steve Thompson,

Acting Manager, Small Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 2010-9027 Filed 4-19-10; 8:45 am]